/Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/Selections/GeometrySelection.h
Note that since the ints are unsigned,IndexConstants::InvalidIDis not directly representable (-1 will become positive 0xFFFFFFFF).
struct FGeoSelectionID
uint32
GeometryID
Geometry ID, stored in lower 32 bits when packed into 64-bits
uint32
TopologyID
Topology ID, stored in upper 32 bits when packed into 64-bits